Can you borrow an xp disc from someone maybe a friends? your not going to be installing windows but it will help you get to the recovery console which is at the beginning of installation of xp.
Can you get into recovery console? if so....
then follow my instructions please here:
When the window opens, look for the box that says Users must use a password.......
If it's checked, uncheck it.
It will then tell you that at least one person has to have a password.
Select the one you want from your user list, and leave the password blank
It might ask for the password again, so just hit enter.
It should boot up and not ask you anymore.